1. Field of the Invention
The present invention relates to spine stabilization and fusion systems and more particularly pertains to a new vertebrae linking system for restricting relative movement between adjacent vertebrae and promoting fusion of the adjacent vertebrae.
2. Description of the Prior Art
The spine of a person is comprised of a series of vertebra arranged in a vertebral column, and each of the vertebrae rests upon a lower vertebra in the vertebral column. Interposed between each pair of adjacent vertebrae is an intervertebral disc that permits a degree of movement of the adjacent vertebrae with respect to each other.
Surgical removal of one or more of the intervertebral discs may become necessary due to damage or deterioration of the discs. If the disc is wholly or partially removed, the spacing between the vertebra must be restored and maintained in the patient after removal in order to maintain the proper alignment and function of the spine.
Numerous techniques and instrumentations have been proposed and developed for restoring and maintaining the proper orientation of the vertebra after disc removal. One preferred procedure is interbody fusion which involves stimulating the fusion of the adjacent vertebrae with bone growth in the space previously occupied by the intervertebral disc. The fusing of the vertebrae with bone thus prevents the relative movement of the adjacent vertebrae that was previously possible with the presence of the disc. The fusing of the adjacent vertebrae in the vertebral column is a gradual process that can take a period of months to years. An important factor in achieving a faster and stronger fusion between the vertebrae is limiting the relative movement between the vertebrae during the period that the vertebrae are fusing together, until the completed vertebrae fusion prevents the relative movement therebetween.
One common technique for stimulating interbody fusion of adjacent vertebrae is the use of structures commonly referred to as "cages". These cage structures are inserted in between the vertebrae after the intervertebral disc has been wholly or partially removed. The surgical insertion of these cages may be performed either anteriorly or posteriorly. Typically, and especially in the case where substantially cylindrical cages are being employed, a portion of the face of each of the vertebrae is removed to form a seat for the cage. Significantly, the bone material removed from the vertebrae includes cancellous autologous bone material, which is typically inserted in the cage to stimulate the fusion of the vertebrae. The cancellous bone material is generally too soft to support and maintain the spacing between the vertebrae, but is highly suitable for stimulating the vertebral fusion when placed in a cage which secures the bone material and maintains the spacing between the vertebrae until fusion is complete.
However, the vertebrae adjacent to the interbody cage may still exhibit some relative movement prior to the fusion of the vertebral bodies together, which may slow down, and in some cases may even prevent, the vertebral interbody fusion from occurring. Various structures have been proposed and developed for attachment to posterior portions of the vertebrae, including the pedicle, the lamina, and the various processes protruding from the vertebral arch of the vertebra. These structures often include rods or plates which bridge between two or more vertebrae, and the rods and plates are typically attached to the vertebrae through the use of screws or cables.
The known structures are typically complex and bulky and require very invasive procedures to mount to the spine, especially when attached to laterally separated portions of the vertebrae such as the transverse and articular processes, and even the lamina and pedicle. Also, the known structures often need to be surgically removed at some future time.
In these respects, the vertebrae linking system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for the purpose of restricting relative movement between adjacent vertebrae and promoting fusion of the adjacent vertebrae.